Then Lanza’s rampage altered the debate in Washington. Suddenly, priority No. 1 wasn’t immigration reform but gun control. The base that had just elected Obama was clamoring for background checks and magazine-clip restrictions, threatening to desert the president before his second inauguration. Many in Washington, including Connecticut’s Democratic senators, were convinced that the much-feared National Rifle Association had become a “paper tiger.” The gun lobby’s muscle hadn’t been truly tested in almost a decade, and NRA head Wayne LaPierre’s bizarre press conference days after the shooting seemed to confirm that the emperor had no clothes.

That meant immigration would have to wait. The clock was ticking on both gun control and immigration, but Democrats moved ahead with gun control first, recognizing that as the memory of the tragedy at Sandy Hook faded, so too would the impetus for new laws. The Senate spent months on a bill, which eventually got whittled down to a universal background-check provision, before it finally died at the hands of a Republican filibuster in mid-April.

In the process, the administration fatally, and irrevocably, antagonized the populist libertarian Right, the same people whom mainstream Republicans and Democrats needed to stay on the sidelines for immigration reform to succeed. By engaging in such an emotional, polarizing issue so early on, Obama poisoned the (admittedly shallow) well of goodwill and the willingness to compromise by Republicans before his term even began in earnest. When a comprehensive immigration bill eventually did pass the Senate in late June with GOP support, the House opposition made clear that the bill had little hope of becoming law.